## Adding Digits

#### Problem

Imagine writing down every possible combination of the digits 1, 2, 3, and 4. What would be the sum of all these combinations?

For example, with the digits 1, 2 and 3; there are six combinations and the sum of these combinations is

123 + 132 + 213 + 231 + 312 + 321 = 1332.

Problem ID: 109 (Mar 2003) Difficulty: 2 Star